Rheostat



June 7,192?c n K 1,631,168 A. E. JWALLER RHEOSTAT Filed May 7, 1924 5 INV NToR y .Ww

BY l sure the making of p Patented June 7, 1927.

UNITED STAT-ES PATENT OFFICE.

ALFRED E. WALLEB, OF IBRONXVILLE, NEW YORK, ASSIGNOB T0 WARD LEONARD ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

BHEOSTAT.

Application nled lay 7,

This invention relates particularly to rheostats in which the resistive conductors are connected to a series of contact buttons, over which a movable contact arm passes for cutting resistance in and out of circuit as desired. The invention not only comrises an improvement in rheostats but also 1n the method of making rheostats.

One object of the invention is to provide an improved method and form of construction which will be economical in cost of material and labor and which may be rapidly and conveniently manufactured. Another object is to provide a construction which will permit the contact buttons to occupy a minimum amount of space. Another object 'is to provide a form of contactbuttons which may be rapidly made automatically in one operation from stock material. Another object is to provide a construction and method of assembly of the contact buttons with the resistive conductors which will inood electrical connection between the con uctors and the contact 2.5, buttons. Another object is to provide a simple form ofconstruction which is well adapted for receiving and electrically connectmg resistive conductors of different sizes and for the connection of the terminal wires to the end buttons, while insuringv good electrical contact of the arts. Other objects and advantages of the invention will be understood from the following description and accompanying drawings which 1llustrate a preferred embodiment thereof.

Fig.' 1 is a plan view, partly broken away, of a rheostat embodying the invention; Fig. 2 is an enlarged cross-section showing a portion of the rheostat plateand one of' the contact buttons and embedding insulation; Fig. 3 is a side view of one form of contact button in its initial state; Fig. 4 is a similar view of another form of contact button in its initial state; Fig. 5 is a plan view of another form of contact button;l Fig.-6 is a side view thereof in its initial state; Fig. 7 is a plan view showingthe method of initial assembly of the contact buttons and resistive conductors; Fig. 8 is a cross-section indicating the method of compressing the contact' butt-ons and Fig. 9 is a similar view showing the method of compressing part onl of a compound contact button.

eferring to Figs. '1 and; 2, a form of rheostat is shown having the well known 19184:. Serial No. 711,584.

metal plate or disk 1 rovided with an upturned edge 2. The e ge 2 is provided with projecting ears which carry the terminals 3. The metal plate is provided witha ground coat 4 of lnsulating material, and an insulating adhesive enamel coating 5 embeds the resistive conductors 6 and the lower portion of the contact buttons 7, as well as a conducting terminal ring 8. A pivoted contact arm 8 carries a conductor bridging the ring 8 and contact buttons 7, so that when the contact armis moved, it will successively cut in or cut out from circuit varying amounts of resistance, as is well understood.

Fi 3, shows a cylindrical form of contact lhaving the body ortion 9, a neck 1() and a lower ring 11, t e lower face ofthe ring 11 having a central depression 12. Fig. 4 shows a simllar contact with an additional neck 10' and an additional ring 11', the outer surface of the latter having the central depression 12.

Considering first the form shown in Fig. 3, the resistive cpnductor isunited therewith by taking the resistive conductor, which has been previously formed of zig-zag shape and bending it atl the desired point around the neck 10 of `the contact button; and then, at the ne'xt desired point of contact of the resistive conductor, placing a portion thereof around the neck of the next contact button and so on. This may be conveniently done by use of a template 13 as shown in Fig. 7. The contact buttons are placed in holes in the template 13 of a proper size and properly placed fol? the particular requirement, the ower ends of the contact buttons being uppermost. The resistive conductor is then bent around the neck of the first contact button, a proper length of conductor then laid out on the` late and bent at its outer end and then le to and passed around the neck `of the next\contact button and so bn until the requisite amount of resistive conductor and number of contact buttons are provided 100 for the particular rheostat desired. In some cases the resistive conductor ma be bent around the .neck of each contact utton be.- fore the same is placed in its hole in the template and in some cases one or more complete 106 l the'face of the ring 11. This compresses the 110 I ring 11 and neck 10 soas .to firmly clamp the vthe ring 11 tends .to avoid the .conductor being forced out of the slot and also permits the ring to be more easily and intimately forced into clo engagement with theconductor. It also rmits a slight spreading of the ring 11 wlthout great exertlon of force giving a `-somewhat larger base portion to the contact button than the remaining art thereof, vas indicated in Fig. 2. This sight spreading of the base permits the enamel coating 5 to more firmly hold thecontact button in sition. If the depression 12 is not provided, more` force will be necessarily given to the plunger 14 in order to secure an intimate en` gement of the conductor with the contact iitton and to secure a sufficient compression and flattening of thc parts. The lunger 14 is shown as adapted to be operate manually by a ivoted arm 15, but obviously' the same may automatically operated in regular sequence at intervals .of time suilcient to permit the operator to place the next' contact under the plunger after the previous one has been compressed. Also a spring release of the plunger may be arranged, whether operated manually or automatically, so as to in-l sure the same amount of force being exerted in compressing each contact button. After compressing thecontact buttonsas described,

they are placed u on the ground coat 4 of the rheostat plate 1n proper relation lto each other and with the conductorsproperly placed -on the ound coat. The parts are then covered with the materialfor forming the enamel and baked ina furnace in the usual manner. The face of the lcontact buttons are then ground' to 'lie in the .same plane for insuring an even and good electrical connection with the contact arm.

Insome cases conductors of different sizes are connected to the same contact button, ror the ends of two conductors of the same size connected. In such cases, especially where portion 9 is made 'a little shorter in this case than when a single neck and single ring is used, so that when compressed,l the total depth of the 'contact buttons will be approximately the same where both forms of contact buttons are used in the same rheostat. Also the terminal wires 16 are usually of copper and of larger sizethan the resistive conductor; and in such a'case the form of contact buttons shown in Fig. 4 is also advantageous, one of the necks receiving the resistive conductor and t e other receiving the terminal conductor. he terminal conductor is usually added to the end button,` or buttons, before the resistiveeonductor has been united with the contact buttons by compression; and in such a case when compressing the contact button which 4'is later to receive the resistive conductor, avsplit washer 17 is in serted around the neck which is later to reoeive the resistive conductor, as shown in Fig. 9. This .contact button can then be eoml pressed to hold' the terminal conductor in place without compressing the parts which are to 'later receive the resistive conductor. The s ilt washer 17 is afterwards removed and t e resistive conductor. placed around the-remaining neck; and the-contact button is a in compressed to'also hold the resistive con uetor in p1ace. Where convenient,- the operation of compressing the contact button having the two conductors thereon, may, of course, be done in one operation instead of successively.

-In' some form of rheostats it is desirable to use a form of contact havin an elongated surface as shown in Figs. 5 and 6. Here the body 9 is shown elongated, 'as likewise the parts 11l and 11", corresponding to the rings 11, 11' of the cylindrical forni of contact. lThe necks l0* and 10 correspond with the necks 10, 10', of the cylindricalcontact, and the lower face of the elongated :form of contact will preferably have formed therein the cent-ral depression 12. ,The method of assembling and compressing the parts is of los course the -samewith elongated form of con.-

tact as with the circular form already described. l

The contact buttons are obviously of a form which permitsthem to' be made rapidly and economically from cylindrical rods for the form shown in Figs. 3 and 4 and from flattened rods for the form shown in Figs. 5 and 6. The buttons are conveniently made in a machine ofthe screw machine type-and all of the parts formed, including cutting olf the buttons', in one operatio This improvement is not onl economical in permitting low cost of material and labor but is particularly advantageous in thereduced size of the contact buttons andspace occupied by them on the, rheostat plate the necessity of extensions from the face f the buttons for connection to the resistive conductor and terminal leads being avoided. The simple method of uniting the conductor with the contact buttons by compression is lio also accomplished quickly and conveniently,

while at. the same time insuring a good electrical connection. i

In some cases the neck of the contact but- `tons may be made eccentric with reference I claim:

1. A rheostat comprising resistive conductors, contact buttons having outwardly extending body portions and having outer contact surfaces, and an insulating coating'for embedding the inner portions of said buttons, said contact buttons having reduced neck portions receiving said conductors and haring inner end portions against said conductors.

A rheostat, comprising resistive conductors, contact buttons, and an insulating coating for embedding the inner portions of said buttons. said contact buttons having a main portion having outer contact surfaces, a reduced portion and a portion compressed against said main portion and against the conductor. L L

3. A rheostat comprising resistive conductors, contact buttons, and an insulating coating for embedding the inner portions of said buttons, said contact buttons having a main v portion having outer contact surfaces. a neck portion near one end thereof and an inner. end portion compressed against said main portion and conductor. 4. A rlieostat comprising resistive conductors', contact buttons, and an insulating coating for embedding the inner portions of said buttons, at least one of said Contact buttons comprising a main portion having outer contact surfaces, a. pluralityof reduced portions, and ,a plurality of portions adjoining the reduced portions and compressed against the conductors andma'in portion.

5. The method of making a rheostat which comprises forming the Contact buttons from a solid piece of material with a reduced compressed neck portion and inner ring port-ion. loopin the resistive conductors around said reduce portions, compressing the inner ring portions against the conductors, and embedding said conductors and compressed portions of said Contact buttons in insulating material. 6. The method of making a rheostat which comprises forming the contact buttons with reduced necks near the ends thereof and with inncrenlarged portions adjoining said necks, looping the resistive conductors around said neck portions, compressing said inner portions against said conductors to enlarge said outer portions, and embedding said conductors and compressed portions of said contact buttons in insulating material. 7.'l`he method of making a rheostat -Wliich comprises forming the-'contact buttons with a reduced neck port-ion and an enlarged portion adjoining said neck, and forming a depression in the. outer surface of said enlarged portion, looping the resistive conductor around said reduced portion, compressing said enlarged portion a ainst the conductor, and embedding the cont uctor and compressed portion in insulating material.

8. The method of niaklng a rheostat which comprises forming a contact button with reduced neck portions and with enlarged portions adjoining said reduced portions,-forming a depression'iny the outer .surface of one lof said enlarged portions, loopingy conductors around said reduced ortions, compressing said enlarged portions against said conductors, and embedding said conductors and compressed portions of said contact button in insulating material.

9. The method of making a rheostat which comprises forming the contact buttons with a main portion, a reduced neck portion and an inner enlarged portion adjoining tlie neck portion.L placing said contact buttons in a template and looping the resistive conductor around said reduced portions, compressing said enlarged portions against said conductor and main portions while positioned in said template, removing said contact lbuttons and conductor from said template and placing them upon an insulating support, and embedding said con-` ductor and compressed portions of said contact buttons in insulating material.

.ALFRED E. WALLER. 

